P R E L I M I N A R Y
sequence. The device continues to access the SecSi data is still “0.” Only erase operations can convert a
Sector region until the system issues the four-cycle
Exit SecSi Sector command sequence. The Exit SecSi
Sector command sequence returns the device to nor-
mal operation. Tables 15 and 16 show the address
and data requirements for both command sequences.
See also “SecSi (Secured Silicon) Sector Flash Mem-
ory Region” for further information. Note that a
hardware reset (RESET#=VIL) will reset the device to
reading array data.
“0” to a “1.”
Unlock Bypass Command Sequence
The unlock bypass feature allows the system to pro-
gram bytes or words to a bank faster than using the
standard program command sequence. The unlock
bypass command sequence is initiated by first writing
two unlock cycles. This is followed by a third write
cycle containing the unlock bypass command, 20h.
That bank then enters the unlock bypass mode. A
two-cycle unlock bypass program command sequence
is all that is required to program in this mode. The first
cycle in this sequence contains the unlock bypass pro-
gram command, A0h; the second cycle contains the
program address and data. Additional data is pro-
grammed in the same manner. This mode dispenses
with the initial two unlock cycles required in the stan-
dard program command sequence, resulting in faster
total programming time. Tables 15 and 16 show the re-
quirements for the command sequence.
Byte/Word Program Command Sequence
The system may program the device by word or byte,
depending on the state of the CIOf pin. Programming
is a four-bus-cycle operation. The program command
sequence is initiated by writing two unlock write cy-
cles, followed by the program set-up command. The
program address and data are written next, which in
turn initiate the Embedded Program algorithm. The
system is not required to provide further controls or
timings. The device automatically provides internally
generated program pulses and verifies the pro-
grammed cell margin. Tables 15 and 16 show the
address and data requirements for the byte program
command sequence.
During the unlock bypass mode, only the Unlock By-
pass Program and Unlock Bypass Reset commands
are valid. To exit the unlock bypass mode, the system
must issue the two-cycle unlock bypass reset com-
mand sequence. The first cycle must contain the bank
address and the data 90h. The second cycle need
only contain the data 00h. The bank then returns to
the reading array data.
When the Embedded Program algorithm is complete,
that bank then returns to reading array data and ad-
dresses are no longer latched. The system can
determine the status of the program operation by
using DQ7, DQ6, or RY/BY#. Refer to the Write Oper-
ation Status section for information on these status
bits.
The device offers accelerated program operations
through the WP#/ACC pin. When the system asserts
VHH on the WP#/ACC pin, the device automatically en-
ters the Unlock Bypass mode. The system may then
write the two-cycle Unlock Bypass program command
sequence. The device uses the higher voltage on the
WP#/ACC pin to accelerate the operation. Note that
the WP#/ACC pin must not be at VHH any operation
other than accelerated programming, or device dam-
age may result. In addition, the WP#/ACC pin must not
be left floating or unconnected; inconsistent behavior
of the device may result.
Any commands written to the device during the Em-
bedded Program Algorithm are ignored. Note that a
hardware reset immediately terminates the program
operation. The program command sequence should
be reinitiated once that bank has returned to reading
array data, to ensure data integrity.
Programming is allowed in any sequence and across
sector boundaries. A bit cannot be programmed
from “0” back to a “1.” Attempting to do so may
cause that bank to set DQ5 = 1, or cause the DQ7 and
DQ6 status bits to indicate the operation was success-
ful. However, a succeeding read will show that the
Figure 3 illustrates the algorithm for the program oper-
ation. Refer to the Erase and Program Operations
table in the AC Characteristics section for parameters,
and Figure 18 for timing diagrams.
July 19, 2002
Am49DL32xBG
27
CYPRESS [ CYPRESS ]
